Check out this concept art from Dr. Horrible's Sing-Along Blog: That's the first sketch of Bad Horse, the mastermind of the Evil League of Evil. Costume designer Shawna Trpcic originally read the script and thought Bad Horse was a person.

It's just one of the weird revelations about the hit webseries that you'll discover in the new book, imaginatively titled Dr. Horrible's Sing-Along Blog: The Book, published by Titan Books. Check out a couple more pages from the book, plus an interview with Dr. Horrible co-creator Zack Whedon, below.

So about the "Bad Horse" art up above — Trpcic tried to design a human supervillain who had a lot of horse imagery and motifs to him. She explains, "I gave him a long braid, like a horse tail, and I tried to bring in elements that to me would say, a 'dark power of the universe,' like the Horses of the Apocalypse. But I didn't think of him as a horse — I thought of him as a person who wreaked vengeance wherever he went. Once I found out it was a horse, I was sort of mortified, and I said, 'Well, should I create metal costume pieces for him? Do you want feathers, or...?' Joss said, 'Shawna, it's a horse. Let it go.'"

The book also includes sheet music, a complete script to both the musical and the commentary track, and loads and loads of pictures and art. There's also a hilarious introduction, round robin-style, by the cast and crew. Plus a personal introduction by Captain Hammer himself, in which he reminisces about "Peggy" and explains where he's been since the story ended. And the Captain's alter ego, Nathan Fillion also contributes a haiku: "Six days to film it/Immortalized as a dick/Then Neil stole my pants."

You get a much clearer look at a lot of the minor characters in the story, including a group portrait of the Evil League of Evil, and there's an afterword by Neil Patrick Harris, and an essay by Felicia Day called "My Horrible Experience."

This is the sort of coffee table book that will make your coffee seem spicier and give your friends something interesting to talk about. It's pretty much a must-have for anybody who enjoyed the original musical.

So we had a chance to ask co-writer Zack Whedon some questions about the book, and how he feels about the musical now:

Now that Dr. Horrible has transformed the media landscape and completely reinvented the supervillain for the 21st century, do you have any regrets about having made supervillains seem so awesome?

None whatsoever. Supervillains have to be awesome to keep the superheroes honest. We do feel bad about transforming the media landscape though. That was uncalled for and not very tastefully done.

Seriously, are you blown away by what an enduring pop culture phenomenon Dr. Horrible has become? And how many memes the series has spawned?

We hesitate to refer to it as a "pop culture phenomenon" but only for a second and then we scream it at the top of our lungs. We are blown away by the response it got and that people continue to care about it and that they want more. It was unexpected, very flattering and loads of fun to watch that all happen. We thought we might be the only ones to care about it and we were fine with that because we were only doing it for the sheer fun of it. I think that ended up coming across on screen. You can sense the camaraderie, the collaborative spirit and that we were, creatively speaking, carefree.

There were two big movies in 2010 that featured supervillains as protagonists: Despicable Me and Mega-Mind. Do you think we're finally ready to love supervillains? Why are supervillains so great?

Supervillains appeal to the same part of us as many superheroes do. They're misunderstood geniuses who never get the girl. Now, we're never going to root for a guy who is going up against Peter Parker but we can root for someone going up against a jock blowhard like Captain Hammer. When you humanize a supervillain they are easy to relate to because they're not the quarterback prom king type, they're the nervous, sweaty, socially awkward, pocket protector type. They're smart and creative. They have to be to pose a threat to their musclebound opponents.

One webseries we're all really excited about that's filming right now is Mortal Kombat, directed by Kevin Tancharoen, brother of Dr. Horrible co-writer Maurissa Tancharoen — do you think Dr. Horrible will have any influence on Mortal Kombat? Will Raiden be doing any singing? (Please?)

I just got off the phone with Kevin and yes, Raiden will be doing a ton of singing. There's little combat at all in fact and none of it is mortal. Also, it mostly revolves around a group of colorful, cloud hopping animals that giggle a lot. It's really a re-imagining of Mortal Combat that is more in the vein of early Care Bears.

None of the above is true. It is going to be harsh and scary and awesome and I can't wait to see it.

Reading the book, you really get the impression that this was a group of family and friends coming together to make something happen. But with a lot of professionals donating their time — was this just like a one-time fluke, due to the Writers Strike, or a model for how stuff can get made in future?

The fact that no one was working definitely made scheduling easier but this is absolutely a model that can be used in the future regardless of whether there are labor disputes afoot. You see this thing all the time actually in web videos. The vast majority of videos are just friends doing some ridiculous thing together in their free time. Funny or Die wouldn't exist if all those hilarious people didn't enjoy goofing off together.

One of the things that really stands out, reading the book, is the way Dr. Horrible comments on celebrity culture. There are the three awesome groupies, plus the newscasters who comment on all the action. Where does that come from?

We do comment on celebrity culture and our collective fascination with their personal lives and how that fascination often obscures actual newsworthy events because it is part of our reality now. The publicity machine functions at such a sophisticated level that we can make people famous for no actual reason. That is interesting and a relatively new aspect of American life and worthy of being mocked. That said, the news media always plays a part in superhero/villain stories so it's also there because it is part of that world whether it's the reverence for Superman or the fear and distrust of Batman. You can't tell one of these stories and leave that aspect out. It also helps push Billy/Dr. Horrible along to have the entire world misreading the situation.

What are you guys working on now?

I, Zack, am working on a feature script right now and once that's complete hopefully I am going to write a comic book for Dark Horse. Jed and Mo are on Spartacus Season 2. Joss has kind of lost it. He wanders around holding a banana like a phone, pretending he's in pre-production on a film version of Avengers for Marvel. Poor guy.

Are we really going to have to wait until after Joss Whedon finishes making the Avengers to get Dr. Horrible 2? Can't we just put that Avengers thing on hold? Can you give us any hints about what to expect in the sequel?

So he is doing that? Wow. I guess we will have to wait. But you know what they say, "When life gives you Avengers, MAKE AVENGERS." The good news is that we will get to see that movie which promises to be amazing. May 2012 cannot come fast enough. Once it does we will get cracking on this DH2 business. I can tell you nothing about it except that it will be a lot of fun to make.